U.S. Pat. No. 6,447,397 discloses a radial detent torque overload clutch primarily suited for a drive line. The clutch has an outer member and an inner member, and three detents between the inner member and the outer member that maintain the members in rotational driving engagement with one another below a certain overload torque between them. Each detent includes a driving member that slides radially in an opening in the inner member between an engaged position in which the driving member is seated in a recess of the outer member in driving engagement with the recess and a disengaged position in which the driving member is retracted from the recess and the outer member is continuously rotatable relative to the inner member. The driving members are moved radially outward to engage in the recesses by a mechanism including a disc spring that exerts an axial spring force that biases the driving members into the engaged position, and the disc spring is regressive so that the spring force it exerts is less in the disengaged position than it is in the engaged position. The disclosure of U.S. Pat. No. 6,447,397 is hereby incorporated by reference for the teaching of the detents in FIGS. 2-6 and operation in col. 4, line 12—col. 5 line 36, as if fully set forth herein.
The design of U.S. Pat. No. 6,447,397 is a relatively large diameter mechanism, which is acceptable in many applications. It was a large diameter in part because of the mechanism that permitted it to be free running for a limited angle so as to permit aligning the splines of the hub with the splines of the shaft to which it is to be connected. However, some applications require a more compact design.